1. The Field of the Invention
The present invention relates to vascular access systems, and more specifically to implantable vascular access ports for use in such systems. The present invention pertains in particular to such vascular access ports as enclose distinct first and second fluid reservoirs and are, therefore, suited for interconnection with a dual lumen catheter when utilized in a vascular access system.
2. Background Art
Implantable vascular access systems are used extensively in the medical field to facilitate the performance of recurrent therapeutic tasks inside the body of a patient. Such a vascular access system generally includes a vascular access port that is attached to the proximal end of a vascular access catheter.
The use of a dual lumen vascular access catheter in such a system enhances the utility of the system by, for example, permitting the withdrawal of fluid through one lumen of the catheter, while affording the opportunity simultaneously to infuse fluid through the other lumen. Medications that react adversely with each other are frequently called for in a course of therapy. The use of a vascular access system having a dual lumen catheter is also particularly advantageous under such circumstances, as each of the incompatible medications can be isolated from the other by consistently using each in a different lumen in the dual lumen catheter of the system. Each medication can then be infused as required in the lumen identified thereto without any risk of adverse reaction with residue of the other medication that might have remained in the system from a previous infusion.
A vascular access port for use in a vascular access system employing a dual lumen catheter typically has a needle-impenetrable housing that encloses distinct first and second fluid reservoirs and defines for each such fluid reservoir a corresponding access aperture that communicates through the housing on the side thereof that is adjacent to the skin of the patient, when the access port has been implanted in the body of a patient. Each access aperture is sealed by a distinct needle-penetrable elastomeric septum.
Such a dual reservoir vascular access port also includes an outlet stem, which projects from the housing of the access port and encloses a longitudinally extending fluid flow passageway corresponding to and communicating with each of the fluid reservoirs in the housing. Using the outlet stem, the distal end of the dual lumen catheter can be mechanically coupled to the access port with each lumen of the catheter in a fluid-tight communication with an individual of the fluid reservoirs therein.
The entirety of the vascular access system, both the dual reservoir vascular access port and the dual lumen catheter attached thereto, is implanted in the body of the patient. The distal tip of the catheter is disposed at a predetermined location where therapeutic activity is to be effected. Once the vascular access system has been implanted, a non-coring hypodermic needle can be employed selectively and repeatedly to access each of the fluid reservoirs of the access port. To do so, the tip of the hypodermic needle is advanced through the skin of the patient at the implantation site for the access port and then used to penetrate a selected one of the septums of the access port itself
The syringe associated with the hypodermic needle can infuse medication or other fluids into the body of the patient at the distal tip of the catheter of the system. Such materials are made to flow down the hypodermic needle from the syringe, through the fluid reservoir accessed by the tip of the hypodermic needle, out of the access port through the corresponding fluid flow passageway in the outlet stem, and along one of the lumens of the dual lumen catheter to the distal tip thereof Alternatively, the syringe is able to aspirate body fluids from the vicinity of the distal tip of the catheter. By withdrawing the syringe of the hypodermic needle, a negative pressure is created in the fluid reservoir that has been accessed. This causes bodily fluids in the vicinity of the distal tip of the catheter to be withdrawn along a lumen of the catheter of the system, into the access port through the outlet stem thereof, and by way of the fluid reservoir being accessed, up the hypodermic needle into the syringe.
Such a dual reservoir vascular access port is illustrated in full detail in U.S. Pat. No. 5,399,168. The dual reservoir vascular access port disclosed therein includes a three-piece needle-impenetrable housing comprising a base, a septum support, and a cap, all configured so as to be capable of being fixedly engaged with each other.
The base has a flat floor and walls normal and upstanding therefrom that define a first fluid reservoir and a second fluid reservoir distinct therefrom.
The septum support is planar and configured to mate with the ends of the walls of the base opposite from the floor of the base. The septum support has formed therethrough a first septum receiving aperture positioned above the first fluid cavity and a distinct second septum receiving aperture positioned above the second fluid cavity.
The cap is configured to receive the septum support and the base, thereby forming the exterior of the upper portion of the housing. The cap includes a top wall and a depending skirt that encloses the septum support and the walls of the base in the assembled condition of the housing. Formed through the top wall of the cap are distinct first and second septum access apertures that are located opposite, respectively, the first and the second septum receiving apertures in the septum support.
An outlet stem enclosing two longitudinally extending fluid flow passageways projects from the base of the housing and through the skirt of the cap. The fluid flow passageways in the outlet stem communicate through corresponding individual exit passageways with individual of the fluid reservoirs in the housing.
In assembling the dual reservoir vascular access port disclosed in U.S. Pat. No. 5,399,168, a pair of identical disc-shaped needle-penetrable elastomeric septums is captured between the septum support and the cap of the housing. Each septum seals a respective fluid reservoir by filling the septum access aperture and septum receiving aperture associated therewith. The dual reservoir vascular access port itself thus includes five (5) components: three (3) needle-impenetrable housing elements and two (2) needle-penetrable septums.
A known dual reservoir vascular access port that attempts to reduce the number of these components is shown in FIG. 1. There can be seen a dual reservoir vascular access port 10 for use in a vascular access system with a dual lumen catheter 12. The coupling of dual lumen catheter 12 to dual reservoir access port 10 is effected by a catheter connection system 14 that is seen in the disassembled state thereof in FIG. 2 to include an outlet stem 16 that is received in the lumens of catheter 12 and a locking sleeve 18 that is slid freely along the outer surface of catheter 12 toward access port 10 and onto the portion of catheter 12 in which outlet stem 16 has been received.
FIG. 2 also illustrates in exploded perspective view the components of access port 10 itself These include a cap 26, a base 20 that encloses a first fluid reservoir 22 and a second fluid reservoir 24, and distinct needle-penetrable elastomeric septums 28, 30 that are disc-shaped. Septums 28, 30 are supported directly on base 20 and retained there by cap 26, sealing access to fluid reservoirs 22, 24, respectively. Septums 28, 30 are exposed to the exterior of access port 10 through respective of septum access openings 32, 34, that are formed through a top wall 36 of cap 26. The tip of a non-coring hypodermic needle is, as a result, capable of accessing either of fluid reservoirs 22, 24 by piercing a corresponding one of septums 28, 30.
Taken alone FIG. 2 would tend to suggest that access port 10 is comprised of only four components: two (2) needle-impenetrable housing elements, and two (2) needle-penetrable septums. This economy in components is, however, actually achieved by constructing base 20 from two (2) separate elements made of dramatically different materials. While cap 26 and most of base 20 are made of injection moldable plastic, outlet stem 16 is fabricated necessarily using the complex machining required with a metallic material, such as titanium. The plastic portion of base 20 is injection molded about outlet stem 16 with outlet stem 16 projecting outwardly from base 20 between fluid reservoirs 22, 24.
The partial breakaway view presented in FIG. 3 depicts outlet stem 16 and the portion of base 20 immediately adjacent thereto. An embedded portion 38 of outlet stem 16 can there be seen to be secured within the material of base 20. This occurs during the injection molding of base 20. Embedded portion 38 of outlet stem 16 extends through the material of base 20 to comprise a portion of the interior sidewalls of each of fluid reservoirs 22, 24. The portion of outlet stem 16 external of base 20 includes a pair of outlet prongs 40, 42 separated by an elongated slot 44.
FIG. 4 reveals the internal structure of outlet stem 16. Fluid flow passageways 46, 48 are formed longitudinally within each of outlet prongs 40, 42, respectively. Fluid flow passageway 46 communicates with first fluid flow reservoir 22 through a rear channel 50 that is entirely formed within embedded portion 38 of outlet stem 16. Similarly, fluid flow passageway 48 communicates with second fluid reservoir 24 through a rear channel 52 that is also formed through embedded portion 38 of outlet stem 16.
Accordingly, access port 10 actually comprises five (5) components: two (2) needle-penetrable septums, two needle-impenetrable plastic housing components, and a metal outlet stem that is partially embedded in one of those housing components. Somewhat disadvantageously, the labor costs associated with the manufacture of a metal outlet stem, such as outlet stem 16, dwarf the labor costs associated with the plastic and needle-penetrable components of access port 10.
As a result, access port 10 is less economical than even the access port disclosed in U.S. Pat. No. 5,399,168 and mentioned previously.